Mg-rich metabasalts from the Southern Musoma –Mara greenstone belt: Possible evidence for mantle plume activity in the Tanzania craton?

Mg-rich metabasalts from the Simba Sirori to Majimoto segment of the southern Musoma-Mara greenstone belt are the most magnesian lavas reported in the Archaean Tanzania Craton. The lavas yielded a Sm-Nd isochron age of 2768 ± 38 Ma (MSWD = 1.2) and corresponding !Nd(2.7 Ga) values in the range of + 0.66 to + 2.81. The lavas exhibit high MgO contents of up to 16 wt %, Cr (140 – 1590 ppm), Ni (80 – 510 ppm), values which are higher than those of primitive NMORB, but are comparable with those of Archaean komatiitic basalts and modern oceanic plateau basalts. Their REE patterns range from the light REE – depleted (La/SmCN = 0.46) to nearly flat (La/SmCN = 0.71 – 1.08) and light REE enriched (La/SmCN = 2.89). They also show negative anomalies of Nb and Ti relative to adjacent elements in multi-element spidergrams. The samples exhibit higher Th/Nb ratios (0.10 – 1.50, mean = 0.39) than those of NMORB (Th/Nb = 0.05) and tend to crustal values (Th/Nb = 0.80)The higher MgO contents of the samples than those of primitive NMORB  requires a mantle source that can generate more magnesian lavas than the depleted mantle and a mantle plume is considered to be a viable source. Thus, the geochemical features of the Mg-rich basalts of Simba Sirori to Majimoto area can be explained by the fact that these rocks were generated by the contamination of komatiitic magmas by the felsic crust. The southern MMGB Mg-rich metabasalts provide a clue to the presence of komatiites, lavas that have not been documented in the Archaean craton of Tanzania. Such magnesian lavas are common in other cratons of the world including Barberton of South Africa, Belingwe of Zimbabwe, and Superior Province of Canada

The origin of late archaean granitoids in the Sukumaland greenstone belt of Northern Tanzania: geochemical and isotopic constraints

Granitoids intruding the late Archaean sequences of the Sukumaland Greenstone Belt of northern Tanzania belong to two distinct geochemical suites. Suite 1 is characterised by Na2O/K2O > 1 (1.04 – 4.67), high Sr/Y (56 – 204) and Ba/Rb ratios (6.1 – 27.1) and low Rb/Sr ratios (0.08 - 0.25). The rocks are enriched in Sr (405 – 1264 ppm) and depleted in Yb (0.17 – 0.93 ppm) and Rb (56 – 132 ppm). On chondrite-normalised REE diagrams, the rocks display highly fractionated patterns characterised by relative LREE enrichment ((La/Yb)N = 23 – 128 and (Gd/Yb)N = 3.10 – 8.54) and lower concentrations of the HREE (YbN = 0.80 – 4.45). On primitive mantle-normalised spidergrams, Nb and Ti, together with P and Y are depleted relative to adjacent elements. The major and trace element characteristics of Suite 1 are comparable to those of typical Archaean TTG suites and High Silica Adakites (HSA). Suite 2 granitoids are characterised by Na2O/K2O < 1, low Sr/Y (2.80 – 41.7) and Ba/Rb (0.40 – 8.91) ratios and high Rb/Sr (0.30 – 6.27) ratios. Suite 2 is also characterised by low Sr (53 - 326 ppm) and high Rb (40 - 365 ppm) and Yb (0.44 – 1.36 ppm) contents. Compared to Suite 1, Suite 2 rocks display less fractionated REE patterns ((La/Yb)N = 15 – 86 and (Gd/Yb)N = 1.73 – 6.74) and are characterised by higher concentrations of the HREE (YbN = 2.1 – 6.5). On primitive mantle-normalised spidergrams, Suite 2 samples, like those of Suite 1, show relative depletion in Th, Nb and Ti, together with P and Y relative to adjacent elements. Sm-Nd mean crustal residence ages for both suites are indistinguishable and range between 2470 and 2720 Ma with a mean of 2610 &#61617; 35 Ma (2 SE), similar to the emplacement age of 2620 &#61617; 40 Ma. The granitoids are interpreted to have formed by partial melting at the base of a late Archaean thickened sub-arc basaltic crust. Melting to form the Suite 1 granitoids occurred in the eclogite stability field whereas Suite 2 formed by melting at shallower depth in the garnet amphibolite stability field. Tanzania Journal of Science Vol. 32 (1) 2006: pp. 75-8

Properties of air-vortex blended yarn influenced by spinning process parameters

225-240Box-Behnken three variables three factors design has been used to optimize the machine spindle diameter, nozzle pressure and yarn delivery speed for achieving the required quality of air vortex polyester/cotton blended yarn. The response surface equations for respective yarn properties in terms of coded factors and significant model terms are developed. Yarn tenacity and elongation show an increase with the increase in nozzle pressure and a decrease with an increase in delivery speed and spindle diameter. Yarn thin places, thick places, neps, U% and hairiness index depict an increase with the increase in delivery speed and spindle diameter, while the decrease is observed with an increase in nozzle pressure. A combination of 1.1mm spindle diameter, 0.5 MPa nozzle pressure and 432.38 m/min delivery speed is the optimized value for targeted yarn quality at 0.71 desirability value

Quantum impurity with 2/3 local moment in 1D quantum wires: an NRG study

We study a Kondo state that is strongly influenced by its proximity to an w^-1/2 singularity in the metallic host density of states. This singularity occurs at the bottom of the band of a 1D chain, for example. We first analyze the non-interacting system: A resonant state e_d, located close to the band singularity, suffers a strong `renormalization', such that a bound state is created below the bottom of the band in addition to a resonance in the continuum. When e_d is positioned right at the singularity, the spectral weight of the bound state is 2/3, irrespective of its coupling to the conduction electrons. The interacting system is modeled using the Single Impurity Anderson Model, which is then solved using the Numerical Renormalization Group method. We observe that the Hubbard interaction causes the bound state to suffer a series of transformations, including level splitting, transfer of spectral weight, appearance of a spectral discontinuity, changes in binding energy (the lowest state moves farther away from the bottom of the band), and development of a finite width. When e_d is away from the singularity and in the intermediate valence regime, the impurity occupancy is lower. As e_d moves closer to the singularity, the system partially recovers Kondo regime properties, i.e., higher occupancy and lower Kondo temperature T_K. The impurity thermodynamic properties show that the local moment fixed point is also strongly affected by the existence of the bound state. When e_d is close to the singularity, the local moment fixed point becomes impervious to charge fluctuations (caused by bringing e_d close to the Fermi energy), in contrast to the local moment suppression that occurs when e_d is away from the singularity. We also discuss an experimental implementation that shows similar results to the quantum wire, if the impurity's metallic host is an armchair graphene nanoribbon.Comment: 13 pages, 20 figure

Properties of air-vortex blended yarn influenced by spinning process parameters

Box-Behnken three variables three factors design has been used to optimize the machine spindle diameter, nozzle pressure and yarn delivery speed for achieving the required quality of air vortex polyester/cotton blended yarn. The response surface equations for respective yarn properties in terms of coded factors and significant model terms are developed. Yarn tenacity and elongation show an increase with the increase in nozzle pressure and a decrease with an increase in delivery speed and spindle diameter. Yarn thin places, thick places, neps, U% and hairiness index depict an increase with the increase in delivery speed and spindle diameter, while the decrease is observed with an increase in nozzle pressure. A combination of 1.1mm spindle diameter, 0.5 MPa nozzle pressure and 432.38 m/min delivery speed is the optimized value for targeted yarn quality at 0.71 desirability value.

Eruption of kimberlite magmas: physical volcanology, geomorphology and age of the youngest kimberlitic volcanoes known on earth (the Upper Pleistocene/ Holocene Igwisi Hills volcanoes, Tanzania)

The Igwisi Hills volcanoes (IHV), Tanzania, are unique and important in preserving extra-crater lavas and pyroclastic edifices. They provide critical insights into the eruptive behaviour of kimberlite magmas that are not available at other known kimberlite volcanoes. Cosmogenic 3He dating of olivine crystals from IHV lavas and palaeomagnetic analyses indicates that they are Upper Pleistocene to Holocene in age. This makes them the youngest known kimberlite bodies on Earth by >30 Ma and may indicate a new phase of kimberlite volcanism on the Tanzania craton. Geological mapping, Global Positioning System surveying and field investigations reveal that each volcano comprises partially eroded pyroclastic edifices, craters and lavas. The volcanoes stand 102 to 106 Pa s) for kimberlite, attributed to degassing and in-vent cooling. Each volcano is inferred to be the result of a small-volume, short-lived (days to weeks) monogenetic eruption. The eruptive processes of each Igwisi volcano were broadly similar and developed through three phases: (1) fallout of lithic-bearing pyroclastic rocks during explosive excavation of craters and conduits; (2) fallout of juvenile lapilli from unsteady eruption columns and the construction of pyroclastic edifices around the vent; and (3) effusion of degassed viscous magma as lava flows. These processes are similar to those observed for other small-volume monogenetic eruptions (e.g. of basaltic magma)

Putting PrEP into Practice: Lessons Learned from Early-Adopting U.S. Providers\u27 Firsthand Experiences Providing HIV Pre-Exposure Prophylaxis and Associated Care

Optimizing access to HIV pre-exposure prophylaxis (PrEP), an evidence-based HIV prevention resource, requires expanding healthcare providers\u27 adoption of PrEP into clinical practice. This qualitative study explored PrEP providers\u27 firsthand experiences relative to six commonly-cited barriers to prescription-financial coverage, implementation logistics, eligibility determination, adherence concerns, side effects, and anticipated behavior change (risk compensation)-as well as their recommendations for training PrEP-inexperienced providers. U.S.-based PrEP providers were recruited via direct outreach and referral from colleagues and other participants (2014-2015). One-on-one interviews were conducted in person or by phone, transcribed, and analyzed. The sample (n = 18) primarily practiced in the Northeastern (67%) or Southern (22%) U.S. Nearly all (94%) were medical doctors (MDs), most of whom self-identified as infectious disease specialists. Prior experience prescribing PrEP ranged from 2 to 325 patients. Overall, providers reported favorable experiences with PrEP implementation and indicated that commonly anticipated problems were minimal or manageable. PrEP was covered via insurance or other programs for most patients; however, pre-authorization requirements, laboratory/service provision costs, and high deductibles sometimes presented challenges. Various models of PrEP care and coordination with other providers were utilized, with several providers highlighting the value of clinical staff support. Eligibility was determined through joint decision-making with patients; CDC guidelines were commonly referenced but not considered absolute. Patient adherence was variable, with particularly strong adherence noted among patients who had actively sought PrEP (self-referred). Providers observed minimal adverse effects or increases in risk behavior. However, they identified several barriers with respect to accessing and engaging PrEP candidates. Providers offered a wide range of suggestions regarding content, strategy, and logistics surrounding PrEP training, highlighting sexual history-taking and sexual minority competence as areas to prioritize. These insights from early-adopting PrEP providers may facilitate adoption of PrEP into clinical practice by PrEP-inexperienced providers, thereby improving access for individuals at risk for HIV

Predictive geochemical mapping using machine learning in western Kenya

Digital soil mapping is a cost-effective method for obtaining detailed information regarding the spatial distribution of chemical elements in soils. Machine learning (ML) algorithms such as random forest (RF) models have been developed for such tasks as they are capable of modelling non-linear relationships using a range of datasets and determining the importance of predictor variables, offering multiple benefits to traditional techniques such as kriging. In this study, we describe a framework for spatial prediction based on RF modelling where inverse distance weighted (IDW) predictors are used in conjunction with auxiliary environmental covariates. The model was applied to predict the total concentration (mg kg-1 ) of 56 elements, soil pH and organic matter content, as well as to assess prediction uncertainty using 466 soil samples in western Kenya (Watts et al 2021). The results of iodine (I), selenium (Se), zinc (Zn) and soil pH are highlighted in this work due to their contrasting biogeochemical cycles and widespread dietary deficiencies in sub-Saharan Africa, whilst soil pH was assessed as an important parameter to define soil chemical reactions. Algorithm performance was evaluated to determine the importance of each predictor variable and the model’s response using partial dependence profiles. The accuracy and precision of each RF model were assessed by evaluating the out-of-bag predicted values. The IDW predictor variables had the greatest impact on assessing the distribution of soil properties in the study area, however, the inclusion of auxiliary values did improve model performance for all soil properties. The results presented in this paper highlight the benefits of ML algorithms which can incorporate multiple layers of data for spatial prediction, uncertainty assessment and attributing variable importance. Additional research is now required to ensure health practitioners and the agricommunity utilise the geochemical maps presented here, and the webtool, for assessing the relationship between environmental geochemistry and endemic diseases and preventable micronutrient deficiency

Implementation of Client-Centered Care Coordination for HIV Prevention with Black Men Who Have Sex with Men: Activities, Personnel Costs, and Outcomes—HPTN 073

Background: Black men who have sex with men (MSM) experience disproportionate rates of HIV infection in the USA, despite being no more likely to engage in sexual risk behaviors than other MSM racial/ethnic groups. HIV pre-exposure prophylaxis (PrEP) has been shown to reduce risk of HIV acquisition; however, rates of PrEP use among Black MSM remain low. Clinical, psychosocial, and structural factors have been shown to impact PrEP use and adherence among Black MSM. Care coordination of HIV prevention services has the potential to improve PrEP use and adherence for Black MSM, as it has been shown to improve HIV-related care outcomes among people living with HIV. Methods: Client-centered care coordination (C4) is a multi-level intervention designed to address clinical, psychosocial, and structural barriers to HIV prevention services for Black MSM within HPTN 073, a PrEP demonstration project among Black MSM in three cities in the USA. The current study examined the implementation process of C4, specifically investigating the activities, cost, time, and outcomes associated with the C4 intervention. Results: On average, participants engaged in five care coordination encounters. The vast majority of care coordination activities were conducted by counselors, averaging 30 min per encounter. The cost of care coordination was relatively low with a mean cost of $8.70 per client encounter. Conclusion: Although client-centered care coordination was initially implemented in well-resourced communities with robust HIV research and service infrastructure, our findings suggest that C4 can be successfully implemented in resource constrained communities

Evaluating the role of quality assessment of primary studies in systematic reviews of cancer practice guidelines

BACKGROUND: The purpose of this study was to evaluate the role of study quality assessment of primary studies in cancer practice guidelines. METHODS: Reliable and valid study quality assessment scales were sought and applied to published reports of trials included in systematic reviews of cancer guidelines. Sensitivity analyses were performed to evaluate the relationship between quality scores and pooled odds ratios (OR) for mortality and need for blood transfusion. RESULTS: Results found that that whether trials were classified as high or low quality depended on the scale used to assess them. Although the results of the sensitivity analyses found some variation in the ORs observed, the confidence intervals (CIs) of the pooled effects from each of the analyses of high quality trials overlapped with the CI of the pooled odds of all trials. Quality score was not predictive of pooled ORs studied here. CONCLUSIONS: Had sensitivity analyses based on study quality been conducted prospectively, it is highly unlikely that different conclusions would have been found or that different clinical recommendations would have emerged in the guidelines